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  • American Institute of Physics (AIP)  (3)
  • Taylor & Francis  (1)
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  • 1
    Publication Date: 2015-01-16
    Description: In standard solar cells, light impinges under a very small angular range, whereas the solar cell emits light into the whole half space. Due to this expansion of etendué, entropy is generated, which limits the maximal efficiency of solar cells. This limit can be overcome by either increasing the angle of incidence by concentration or by decreasing the angle of emission by an angularly confining element or by a combination of both. In an ideal solar cell with radiative recombination as the only loss mechanism, angular confinement and concentration are thermodynamically equivalent. It is shown that concentration in a device, where non-radiative losses such as Shockley-Read-Hall and Auger recombination are considered, is not equivalent to angular confinement. As soon as non-radiative losses are considered, the gain in efficiency due to angular confinement drops significantly in contrast to the gain caused by concentration. With the help of detailed balance calculations, it is furthermore shown that angular confinement can help to increase the efficiency of solar cells under concentrated sunlight even if no measurable gain is expected for the solar cell under 1-sun-illumination. Our analysis predicts a relative gain of 3.14% relative in efficiency for a realistic solar cell with a concentration factor of 500.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 2
    Publication Date: 2016-05-13
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 3
    Publication Date: 2015-10-28
    Description: The performance of large negative ion sources used in neutral beam injection systems is in long pulses mainly determined by the increase of the currents of co-extracted electrons. This is in particular a problem in deuterium and limits the ion currents which are for long pulses below the requirements for the ITER source. In the source of the ELISE test facility, the magnetic field in front of the first grid, which is essential to reduce the electron current, is generated by a current of several kA flowing through the plasma facing grid. Weakening of this field by the addition of permanent magnets placed close to the lateral walls has led to a reduction of the electron current by a factor three without loss of ion current when source was operated in volume production. If this effect can be validated for the cesiated source, it would be a large step towards achieving the ITER parameter in long pulses.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 4
    Publication Date: 2019-01-24
    Description: The presented study assessed the heavy metal contamination risk in a former sludge deposit field of the River Ruhr in Essen, Germany. Therefore, the temporal and spatial distribution in soils and plants, chemical fractionation, mobilization potential, and transfer characteristics have been investigated. Soil samples, roots and shoots of rushes (Juncus sp.), and stem wood disks of willows (Salix sp.) were analyzed for Zn, Cu, Pb, Ni, Cr, and Cd. Plant available and mobile heavy metal portions have been determined using a sequential extraction procedure. The results show that the soils and the rushes are highly contaminated, although there is a considerable decrease compared to initial concentrations some 20 years ago. The willows show only small heavy metal enrichment. pH induced mobilization potential in soil is high for Cd, Zn and Ni. Additionally, these elements contain high portions of plant-available fractions. High transfer rates from soil to roots and very high rates from roots to shoots of rushes have been determined for Cd and Zn, indicating an accumulation of these elements in shoots of rushes. The rushes reflect the temporal and spatial heavy metal distribution in soil and might thus be used as a bioindicator or for phytoremediation.
    Type: Article , PeerReviewed
    Format: text
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